MV transport by EmrE. Radiolabelled, 14C MV2+ transport into E. coli lipid vesicles by EmrE over time. EmrE reconstituted into E. coli lipid vesicles extruded to (■), 50 nm; (○), 200 nm and (▲), sonicated lipid vesicles. Control data is shown for (□), absence of a pH gradient and (◆), absence of protein in 50 nm lipid vesicles. Errors are shown as first standard deviation of 3 measurements on different protein preparations (with each value used for each protein preparation, for each data point shown, also being the average of 3 measurements on that particular preparation).